Critically ill patients are often found to have infections with normal enteric organisms. These infections have been proposed to occur as a consequence of bacterial translocation (the transit of viable microbes from the gut lumen across the intestinal barrier). Of importance in the process of bacterial translocation is the initial interaction of the bacteria with the enterocyte. Cell surface adhesion molecules are increasingly recognized to play a role in the host-bacterial interactions. We will investigate the hypothesis that host cell surface molecule expression modulates bacteria enterocyte interactions, and that the integrins are important in these interactions. The specific aims of this proposal are to transfect Caco-2 enterocytes with integrin subunit cDNA, to characterize adhesion molecule distribution on transfected enterocytes, to characterize barrier integrity of confluent cultures of transfected enterocytes, and to characterize bacteria-enterocyte interactions with transfected enterocytes. Enterocytes will be transfected with constructs, for expression of integrin alpha2 and alpha3 subunit cDNA in the sense and antisense orientations, thereby expressing increased (sense) or decreased (antisense) alpha2 or alpha3 integrin subunit. Preliminary data indicates that enterocytes internalize bacteria at lower rates when the alpha2 integrin subunit is overexpressed. The effects of integrin expression will be evaluated structurally (by examining the ultrastructural topography and subcellular architecture of these interactions), functionally (by measuring bacterial binding, internalization and intracellular survival), and from the aspect of enterocyte phenotypic alterations (by epifluoresence microscopy, flow cytometry, transmembrane electrical resistance, and fluorescent dextran particle flux). These investigations will further the understanding of bacteria-enterocyte interactions, and may lead to novel therapeutic and prophylactic approaches toward nosocomial infections in high risk surgery and trauma patients.